The present invention relates to a semiconductor laser apparatus, and more particularly relates to, as one example, a semiconductor laser apparatus for use in an optical pickup apparatus for recording data on optical recording media typified by optical disks and for reading the recorded data.
Conventionally, there are two types of optical pickup apparatus for read and write access to optical disks such as CD-ROMs (Compact Disk—Read Only Memories), MDs (Mini Disks) and DVDs (Digital Versatile Disks).
They are: a discrete-type optical pickup apparatus discretely assembled from a single semiconductor laser apparatus mostly of a so-called CAN type in a size of φ 5.6 mm, an optical component and a signal detection element; and an optical pickup apparatus with use of a so-called hologram laser constituted by integrating a diffraction grating, a signal detection element and a semiconductor laser device.
It is to be noted that in recent years, in addition to the single semiconductor laser apparatuses such as those of the CAN type, frame-type semiconductor laser apparatuses pursuing lower costs are gaining access to the market.
FIG. 5 shows a CAN-type semiconductor laser apparatus and FIG. 6 shows a frame-type semiconductor laser apparatus.
FIG. 5 illustrates a partial cross section of the CAN-type semiconductor laser apparatus to show its inner constitution. As shown in FIG. 5, a cap 102 is fixed onto a stem 105 that is an eyelet portion for covering a stem block 107, a semiconductor laser device 103 fixed onto the stem block 107 and a monitor photodiode 106. The ceiling of the stationary-side mold 102 is a cap glass 101.
Further, a wire 108a electrically connects the monitor photodiode 106 to a lead pin 109a, while a wire 108b electrically connects the semiconductor laser device 103 to a lead pin 109b. 
Description is now given of a frame-type semiconductor laser apparatus shown in FIG. 6. In a cost conscious view point, a mainstream apparatus among these frame-type semiconductor laser apparatuses is so-called “open type” which exposes semiconductor laser devices and wire bonding interconnections as shown in FIG. 6.
The frame-type semiconductor laser apparatus 210 shown in FIG. 6 has a resin base portion 200 produced from resin materials and lead frames 207a, 207b, 207c. The resin base portion 200 has a disc-like stand portion 202 and a half-column-like support portion 201 set on the stand portion 202. The lead frames 207a, 207b, 207c are embedded in a flat face 201a of the support portion 201 with a bonding surface being exposed.
A semiconductor laser device 205 is fixed onto the exposed face of the lead frame 207b, and the semiconductor laser device 205 is electrically connected to the lead frame 207c via a wire 206.
It is to be noted that although FIG. 6 shows a plural sets of lead frames 207a to 207c in the state of being connected to a frame base portion 207, respective lead frames 207a to 207c are separated from the lead frame base portion 207 and individual semiconductor laser apparatuses 210 are completed.
In the case of the CAN-type semiconductor laser apparatus shown in FIG. 5, the semiconductor laser apparatus is positioned and fixed by inserting the stem 105 made of a round-shaped metal plane plate portion typically called an eyelet portion into a housing of the optical pickup apparatus.
Consequently, if the semiconductor laser apparatus of FIG. 5 is adopted, it is difficult to set the size (thickness) of the housing of the optical pickup apparatus smaller than the diameter of the eyelet, which works against developing thinner optical pickup apparatuses.
Moreover, in view of radiation characteristics, heat of the semiconductor laser device 103, which is a heat source, is once transferred to the stem 105 through the stem block 107 incorporating the semiconductor laser device 103, and then is conducted to the housing of the optical pickup apparatus. This lengthens a radiation route and therefore disturbs improvement of the radiation characteristics.
Further, in the former semiconductor laser apparatus in FIG. 5, changing the material of the stem (eyelet portion) 105 which is typically made of steel into copper allows heat conduction characteristics to be increased. However, the stem 105 made of copper leads to low resistance of the stem 105, thereby causing a problem that the cap 102 cannot be welded to the stem 105 through resistance welding.
In the latter frame-type semiconductor laser apparatus 210 shown in FIG. 6, the lead frame base portion 207 is used for connecting multiple devices to achieve reduction in manufacturing costs.
However, in the frame-type semiconductor laser apparatus 210, because of its constitution, insulation performance among the lead frames 207a to 207c is achieved by integrally forming the resin base portion 200 with the lead frames 207a to 207c with use of a resin material which is poorer in heat conduction characteristics for 1 digit or more than metal.
Therefore, it is also difficult for the frame-type semiconductor laser apparatus 210 to improve the radiation characteristics.
In recent years, under these circumstances, low-profile, small-size, lower-cost and higher-output optical disk drives are intensely demanded, and so the semiconductor laser apparatuses of the matching qualities for use in combination therewith are also demanded.
In the light of this situation, the semiconductor laser apparatuses particularly supporting low-profile and high-output specifications, i.e., the semiconductor laser apparatuses having sufficient package radiation characteristics are demanded.